Method of measuring meat texture

ABSTRACT

In a method of detecting meat texture the surface of the meat is illuminated in at least two directions which are substantially perpendicular to a base for the meat in a common illumination plane. A loose texture manifests itself in deep cracks (8, 9, 10) in e.g. the fillet of fish. When the surface of the fillet is illuminated in the directions (11 and 12), the depressions (8, 9, 10) bring about such a great contrast in the recording of an image of the surface that the image information can be processed electronically and be utilized for control of equipment, either for rejection of the fillet or for cutting away the damaged areas.

The invention concerns a method of detecting meat texture, i.e. thefirmness and coherence of the meat. Today, cooking of food productstakes place automatically to a great extent, so that meat with a loosetexture can be torn to pieces and thus cannot any more be accepted as afirst-class product.

The object of the invention is to provide a method by means of which thetexture may be detected automatically and without contact while themeat, e.g. a fillet of fish, is advanced on a conveyor.

This is obtained by performing the method as stated in thecharacterizing portion of claim 1, it having been found that withcorrect setting of the said acute angles with respect to the size andthe type of the cracks in the meat which must be expected in themeasurement, a surprisingly reliable measure of the extent of suchcracks transversely to said illumination plane may be achieved.

In connection with detection of quite different phenomena, such asmicroscopic cracks or measuring of outer contours, it is known toilluminate the object and to record the image information, see e.g. DEOS Nos. 2 843 257 and 3 413 027. This prior art is relativelysophisticated, using i.a. special wavelengths for the light, and inrelation to this the invention consists in realizing that the opposite,viz. simplification of the art, lends itself particularly well preciselyfor detection of meat texture.

More particular, the relatively deep cracks in meat having a poortexture involves good contrast formation, in particular when the cracksextend predominantly transversely to a plane thorugh the sources oflight.

When measuring the texture of fish meat, which is a primary object ofthe invention, it should be noted that cracks in the longitudinaldirection of a fillet of fish, i.e. substantially in parallel with thelongitudinal fibres, are not indicative of a loose texture, whereascracks transversely to the longitudinal fibres directly indicate a loosetexture and a poor meat quality. Accordingly, for measuring the textureof fish meat, the method is advantageously performed as stated in claim2.

Thus, the invention is based on the finding that the above-mentionedillumination and image recording may be utilized as an expression of thetexture of the meat, but the surprisingly good results are also due to aspecial utilization of the video information processing, known per se,for precisely this object. When the method is performed as stated inclaim 3, the method may thus be improved additionally by usingelectronic contrast intensification, e.g. of the type disclosed in thebook "From image to surfaces" by William Erik Leifur Grimson, M.I.T.1981, p. 16-100.

The utilization of the digetal technique in connection with theinvention also entails that the invention is preferably performed asstated in claim 4. The positional information thus provided is thentransferred to e.g. a robot controlled water jet cutting apparatus whichautomatically cuts away the parts of the fillet where the meat is looseand incoherent.

The invention will be explained more fully by the following descriptionof an embodiment with reference to the drawing, in which

FIG. 1 schematically shows a fillet of fish having a satisfactorytexture,

FIG. 2 shows a section through the fillet from FIG. 1 and schematicallyshows an embodiment of illumination directions and recording directionfor image information,

FIG. 3 schematically shows a fillet of fish having a dissatisfactorytexture,

FIG. 4 is a section through FIG. 3 corresponding to FIG. 2, and

FIG. 5 in principle shows an apparatus for performing the method of theinvention.

In FIG. 1, the numeral 1 represents the contour of a fillet of fishhaving in the longitudinal direction some grooves 2, 3 in the meatsubstantially in parallel with the longitudinal direction of the fillet.

In FIG. 2, the fillet is shown resting on a base 4, and arrows 5, 6indicate illumination directions for recording of image information bymeans of a video camera shown schematically at 7. Seen in thelongitudinal direction of the fillet, the surface of the fish isrelatively even and has only small elevations and depressions which willnot result in a noticeable contrast to the shown illuminationdirections, which form predetermined acute angles with the base 4. Inthe embodiment shown, these illumination directions form substantiallyuniform acute angles with the base 4, which may vary, however, dependingupon the type of meat which is to be examined. The optical axis of theimage apparatus 7 will be essentially parallel with the illuminationplane defined by the illumination directions 5 and 6 and be essentiallyparallel with the angle bisector for these illumination directions.

FIG. 3 shows a fillet of fish having a loose texture, which involvesdeep grooves or cracks 8-10 extending predominantly transversely to thelongitudinal direction of the fillet. FIG. 4 shows the same as FIG. 2,but it is noted now that the illumination directions 11, 12 entail thatdark regions occur in the bottom of the cracks 8-10, because the lightfalls as indicated by the broken lines in the figure. When an image istaken of the fillet from FIG. 4, information will thus be obtained onthe extent of such transverse cracks.

It will be appreciated that the depth and the width and optionally apreferred inclination of the cracks to be detected are important for theselection of the optimum illumination directions 11 and 12. Thus, it iswithin the scope of the invention to change the illumination directionsin accordance with the product to be examined. It will likewise beappreciated that several recordings may be taken on the same object withmutually differently positioned illumination planes and associatedrecording directions.

FIG. 5 schematically shows an apparatus for performing the method,comprising a recording station 13 mounted on a table 14 which preferablycontains data processing equipment for processing the video informationwhich is obtained by means of a camera. The recording equipment 13 maybe adjustable in various ways, and the lamps 16, 17 shown are movablysecured on a pair of arms 18, 19.

The numeral 20 represents a conveyor for fillets of fish, such as thefillet 21. As soon as an image of the surface of the fillet has beenrecorded, the video information is processed in the data processingequipment for producing texture information. The information may bedisplayed on a video display and may form the basis for automaticremoval of the fillet from the conveyor if the quality is below acertain level. Alternatively, the image information may comprisepositional information which is transferred to a cutting apparatus 22with a cutting robot 23, which, e.g. by means of a water jet, cuts awayprecisely those portions of the fillet which have a too loose texture.

Thus, the method described permits fully automatic sorting or subsequentprocessing of fillets of fish so that a higher production rate andimproved product quality are obtained.

We claim:
 1. A method of detecting meat texture, characterized byilluminating the surface of the meat by means of angularly adjustableuniform sources of light in at least two directions which, in a commonillumination plane substantially perpendicular to a base for the meat,form acute angles with the base, and producing image information of theilluminated surface by means of a single camera seen from an area in thevicinity of the illumination plane and the angle bisector plane for saidillumination directions.
 2. A method according to claim 1 and fordetection of fish meat texture, characterized by placing the fish meaton the base so that the longitudinal fibres of the meat are parallelwith the illumination plane.
 3. A method according to claim 1, whereinthe image information is produced by means of a video camera,characterized by intensifying contrasts in the image information bymeans of electronic signal processing, known per se, of the videoinformation.
 4. A method according to claim 3, characterized byproducing from the image information positional information on imagecontrasts which are greater than a predetermined value.